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#epiblast

2 public questions tagged with this topic.

Chick development-ll

Chick embryo epiblast cells are precursors for:

Classic fate mapping using carbon particles and fluorescent dyes shows chick epiblast before gastrulation is pluripotent sheet. Single labelled epiblast cells can contribute descendants to neural ectoderm, epidermis, all mesodermal subtypes including paraxial, lateral, extraembryonic and definitive endoderm depending on ingress timing through streak. Hypoblast only yields extraembryonic yolk sac endoderm that eventually replaced. Thus epiblast at stages X-XIII harbors progenitors for all three germ layers, reflecting epiblast as embryonic source homologous to amphibian animal and marginal zones combined, not restricted to only one layer.

Ref: Wolpert, Principles of Development, Chapter 5: Chick epiblast fate as precursor of all germ layers.

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Fertilization in mammals-ll

Epiblast cells eventually form:

After segregation of hypoblast, remaining inner cell mass cells constitute epiblast, a columnar pluripotent epithelium expressing Oct4 Nanog and Fgf4, forming embryonic disc. Epiblast gives rise to entire embryo proper through gastrulation generating definitive ectoderm, mesoderm and endoderm, while also producing amniotic ectoderm and extraembryonic mesoderm contributing to chorion and amnion. Hypoblast and trophoblast remain extraembryonic. Therefore epiblast represents founder population of fetal body, preserving developmental potency until gastrulation signals direct trilaminar differentiation, axis patterning, organogenesis for complete organism formation and tissue specification.

Ref: Marikawa & Alarcon, Cold Spring Harb Perspect Biol: Epiblast origin of embryo proper and germ layer formation.

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